1. Field of the Invention
The present invention relates to a display device, and particularly to a display device that can improve display quality.
2. Description of the Related Art
In recent years, as one of flat panel displays (FPD), attention is increasingly focused on an organic EL (electroluminescent) display device using an organic EL element, and the organic EL display devices are being actively developed.
Under the present circumstances, liquid crystal displays (LCD) are the mainstream of flat panel displays. However, because the liquid crystal display is not a device using a self-luminous device and the liquid crystal display needs lighting members such as a backlight and polarizers, the liquid crystal display has problems that the device thickness increases and the brightness is short. In contrast to this, because the organic EL display device is a device using a self-luminous device, the organic EL display device is more advantageous than the liquid crystal display in that the organic EL display device does not need a back light, for example, in principle, the device thickness can be reduced, and high brightness can be obtained.
Particularly, in a so-called active matrix-type organic EL display device formed with TFT circuits for individually switching pixels, each pixel can hold a charge for emission, whereby the power consumption can be suppressed. In addition, the active matrix-type organic EL display device is being actively developed because the active matrix organic EL display device can be relatively easily provided with a large screen and higher definition as well, and the active matrix organic EL display device is expected to be the mainstream of next generation flat panel displays.
In the organic EL display device, in fabricating a pixel array unit in which a plurality of pixels is arranged in a matrix, an anode is deposited, a pixel separation film is formed to individually separate the pixels from each other, an organic film of each of the pixels is then vapor deposited, and a cathode is deposited on it. At this time, the pixel array unit is formed such that the organic films have a multi-layer structure. However, leakage current sometimes occurs between the anode and the cathode through a so-called hole injection layer provided between the anode and the organic film.
In the past, a leakage path that is a channel through which leakage current is carried is varied depending on the deposition order of organic films, and the variation of the leakage paths causes a difference in the flow rate of leakage current. On this account, the current carried through each of the organic films is varied, which causes a color shift to degrade the display quality of the organic EL display device.
For example, JP-A-2000-195677 (Patent Document 1) discloses an organic EL display device in which pixels are separated into a plurality of pixel elements by a pixel separation structure that is a three-dimensional structure having an overhang unit.